The effect of gestational parity on FEV₁ in a group of healthy volunteer women

In the past, studies utilizing within-subject comparisons of small groups of pregnant women showed that forced expiratory volume in 1 s (FEV₁) remained essentially unchanged during pregnancy. However, one of the findings from an epidemiological study was that women with greater number of children experienced a faster decline of FEV₁. The aim of this study was to examine the effect of parity on FEV₁ in a group of healthy volunteer women. To this end, cross-sectional multiple regression analyses of data from 397 healthy women participants in the Baltimore Longitudinal Study of Aging (BLSA) with a mean (range) age of 47.7 (18-92) years were performed. Similar analyses were done using the younger (50 years or less) and the older (> 50 years) subgroups. After controlling for age, height, weight, and smoking, parity as a dichotomous variable was associated with a higher FEV₁ in women of child-bearing age (0.139 l; P = 0.02) but not in the older women. There was a modest link with the number of children (P = 0.05), with the first child possibly having the greatest effect on FEV₁. We could not account for the effect of parity on FEV₁ by the educational level, occupation, health status of the women, or by the presence of a cohort effect. Thus the nulliparous state is associated with lower FEV₁ in this group of healthy adult women of child-bearing age.